Here is how it works:
Immagine to have a DOM element in your page that is a place holder for a component, in this element you can add an attribute in some namespaces (eg. ext) and put a json encoded string in.

Example:

Code:

<div id="component" ext:config="{width:400,cls:'test'}" ></div>

In this example we'll pass the arguments width: 400 and cls: 'test' to the constructor of the new class.